Simulation numérique des écoulements turbulents dans les canaux de refroidissements (Application aux moteurs-fusées)

Cette thèse traite par simulation numérique les écoulements turbulents compressibles avec transferts de chaleur, en relation avec les applications moteurs-fusées. Elle concerne, plus particulièrement, les systèmes de refroidissement des chambres de combustion. Le fluide refroidissant circule dans un état supercritique (haute pression et basse température) dans des canaux millimétriques, entourant la chambre de combustion. Ces problèmes font appel à une physique assez complexe et mettent en jeu un couplage fort entre les aspects compressibles et les transferts thermiques, en plus des phénomènes liés à la thermodynamique supercritique. D un point de vue numérique, deux solveurs spécifiques ont été utilisés dans le cadre de cette thèse. Il s agit, d une part, du code CHOC-WAVES développé au CORIA pour la partie compressible et onde de choc et, d autre part, le code PPMBFS développé à l Université de Pennsylvanie (USA) pour les applications supercritiques et avec une thermodynamique variable. Sur le plan de la modélisation physique, l approche LES a été utilisée, en appui des simulations DNS. Dans ce contexte, un modèle de sous-maille thermique, pour la prise en compte du Prandtl turbulent variable, a été intégré et validé. Les résultats obtenus, dans le cadre des LES et DNS d un canal supersonique refroidi, ont permis de mieux analyser les corrélations aérothermiques ainsi que les structures cohérentes présentes au sein de cet écoulement. En particulier, il a été montré les limites de l hypothèse de l Analogie Forte de Reynolds (SRA) dans le cas d écoulements fortement anisothermes, et le rôle joué par les structures tourbillonnaires dans l accentuation des transferts pariétaux. La problématique des gaz réels a été ensuite examinée dans le cadre d un canal industriel (en l occurence EH3C). Cette étude a permis de mettre en évidence les difficultés (à la fois numérique et physique) liées à ce type d écoulement. Les différentes investigations ont permis de fournir des informations utiles, notamment en ce qui concerne la phénoménologie des structures cohérentes et les différentes corrélations aérothermodynamiques.This research deals with the numerical simulation of compressible turbulent flows with heat transfers, applied to rocket engines. It relates more particularly the cooling of combustion chambers, in which a fluid flows in a supercritical state (high pressure and low temperature) inside millimeter channels. These problems involve complex physical phenomena and coupling between compressible aspects and heat transfer phenomena as well as supercritical thermodynamics. From a numerical point of view, two specific solvers have been used in the context of this thesis. The first code (CHOC-WAVES) has been developed in the CORIA lab for compressible flows and shock waves. The second one (PPMBFS) has been developed at the Pennsylvania University for applications with supercritical thermodynamics variables. In terms of physical modeling, the LES approach has been widely used in support of DNS. In this context, a thermal subgrid model using a variable turbulent Prandtl number has been integrated and validated. A supersonic cooled channel has been simulate dusing both LES and DNS techniques and its results have been carefully analysed through the aerothermics correlations and coherent structures. In particular, it has been shown that the Strong Reynolds Analogy hypothesis (SRA), in the case of a strongly anisothermal flow is not valid anymore. The wall heat flux had an impact on the coherent structures. The issue of real gases was then examined through the industrial channel flow simulation (EH3C). This study has high lighted the difficulties (both numerical and physical) associated with this type of flow. The various investigations have provided useful information, especially regarding the phenomenology of coherent structures and various aerothermodynamics correlations.ROUEN-INSA Madrillet (765752301) / SudocSudocFranceF

Creating and sustaining stakeholder emotional resonance with organizational identity in social mission-driven organizations

How do senior managers of social mission-driven organizations build and sustain stakeholders’ emotional resonance with organizational identity beliefs over time in the face of repeated existential threats? This is an important question, given the dependence of many such organizations on external stakeholders who provide the resources necessary for survival. In this paper, we investigate the case of Solidum, a philanthropic organization devoted to poverty causes. Drawing on ethnographic, interview and archival data over 20 years, we develop a process model showing how senior managers may create and sustain stakeholder emotional resonance through three practices of emotional resonance work: building emotional bridges, enrolling stakeholders in collective soul-searching and materializing an appealing identity symbol. We show that stakeholder emotional resonance needs to be continually renewed and reshaped in the face of ongoing challenges associated with macro-organizational trends and the routinization of existing practices that can result in the dissipation of emotional resonance over time. The paper contributes to the literature on organizational identity maintenance by drawing attention to the active managerial work required to sustain stakeholder emotional resonance over time to allow mission-driven organizations to survive and prosper

Comparative efficacy and safety of bimekizumab in axial spondyloarthritis: a systematic literature review and network meta-analysis

OBJECTIVES: To compare the efficacy and safety of bimekizumab 160 mg every 4 weeks, a selective inhibitor of interleukin‑17F and 17A, with biologic/targeted synthetic disease-modifying anti-rheumatic drugs (b/tsDMARDs) in non-radiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS). METHODS: A systematic literature review identified randomised controlled trials until January 2023 for inclusion in Bayesian network meta-analyses (NMAs), including three b/tsDMARDs exposure networks: predominantly-naïve, naïve, and experienced. Outcomes were Assessment of SpondyloArthritis international Society (ASAS)20, ASAS40, and ASAS partial remission (PR) response rates at 12-16 weeks. A safety NMA investigated discontinuations due to any reason and serious adverse events at 12-16 weeks. RESULTS: The NMA included 36 trials. The predominantly-naïve network provided the most comprehensive results. In the predominantly-naïve nr-axSpA analysis, bimekizumab had significantly higher ASAS20 response rates vs secukinumab 150 mg (with loading dose [LD]/without LD), and comparable response rates vs other active comparators. In the predominantly-naïve AS analysis, bimekizumab had significantly higher ASAS40 response rates vs secukinumab 150 mg (without LD), significantly higher ASAS-PR response rates vs secukinumab 150 mg (with LD), and comparable response rates vs other active comparators. Bimekizumab demonstrated similar safety to other b/tsDMARDs. CONCLUSION: Across ASAS outcomes, bimekizumab was comparable to most b/tsDMARDs, including ixekizumab, TNF inhibitors and upadacitinib, and achieved higher response rates vs secukinumab for some ASAS outcomes in predominantly b/tsDMARD-naïve nr-axSpA and AS patients at 12-16 weeks. In a pooled axSpA network, bimekizumab demonstrated comparable safety vs other b/tsDMARDs

Targeting Hsp27/eIF4E interaction with phenazine compound: A promising alternative for castration-resistant prostate cancer treatment

The actual strategy to improve current therapies in advanced prostate cancer involves targeting genes activated by androgen withdrawal, either to delay or prevent the emergence of the castration-refractory phenotype. However, these genes are often implicated in several physiological processes, and long-term inhibition of survival proteins might be accompanied with cytotoxic effects. To avoid this problem, an alternative therapeutic strategy relies on the identification and use of compounds that disrupt specific protein-protein interactions involved in androgen withdrawal. Specifically, the interaction of the chaperone protein Hsp27 with the initiation factor eIF4E leads to the protection of protein synthesis initiation process and enhances cell survival during cell stress induced by castration or chemotherapy. Thus, in this work we aimed at i) identifying the interaction site of the Hsp27/eIF4E complex and ii) interfere with the relevant protein/protein association mechanism involved in castration-resistant progression of prostate cancer. By a combination of experimental and modeling techniques, we proved that eIF4E interacts with the C-terminal part of Hsp27, preferentially when Hsp27 is phosphorylated. We also observed that the loss of this interaction increased cell chemo-and hormone-sensitivity. In order to find a potential inhibitor of Hsp27/eIF4E interaction, BRET assays in combination with molecular simulations identified the phenazine derivative 14 as the compound able to efficiently interfere with this protein/protein interaction, thereby inhibiting cell viability and increasing cell death in chemo- and castration-resistant prostate cancer models in vitro and in vivo

Photoemission-time-delay measurements and calculations close to the 3s-ionization-cross-section minimum in Ar

We present experimental measurements and theoretical calculations of photoionization time delays from the 3s and 3p shells in Ar in the photon energy range of 32-42 eV. The experimental measurements are performed by interferometry using attosecond pulse trains and the infrared laser used for their generation. The theoretical approach includes intershell correlation effects between the 3s and 3p shells within the framework of the random-phase approximation with exchange. The connection between single-photon ionization and the two-color two-photon ionization process used in the measurement is established using the recently developed asymptotic approximation for the complex transition amplitudes of laser-assisted photoionization. We compare and discuss the theoretical and experimental results, especially in the region where strong intershell correlations in the 3s -> kp channel lead to an induced "Cooper" minimum in the 3s ionization cross section

A 36 ka environmental record in the southern tropics : Lake Tritrivakely (Madgascar) (Un enregistrement de l'environnement depuis 36 ka en zone tropicale sud : le lac Tritrivakely (Madagascar)).

The upper 13 m of a 40 m-long sedimentary profile core taken in a crater lake on the Malagasy Plateau reveals 36,000 yrs of hydroclimatic evolution. A shallow lake occupies the core site from ≃35 to ≃19 ka BP under climatic conditions cooler than today. The water table is very low and biological productivity extremely reduced during the Last Glacial Maximum. A large warming was initiated at ≃14.5 ka BP. The modern bog establishes about 4 ka ag

Complete Ascertainment of Intragenic Copy Number Mutations (CNMs) in the CFTR Gene and its Implications for CNM Formation at Other Autosomal Loci

Over the last 20 years since the discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, more than 1,600 different putatively pathological CFTR mutations have been identified. Until now, however, copy number mutations (CNMs) involving the CFTR gene have not been methodically analyzed, resulting almost certainly in the under-ascertainment of CFTR gene duplications compared with deletions. Here, high-resolution array comparative genomic hybridization (averaging one interrogating probe every 95 bp) was used to analyze the entire length of the CFTR gene (189 kb) in 233 cystic fibrosis chromosomes lacking conventional mutations. We succeeded in identifying five duplication CNMs that would otherwise have been refractory to analysis. Based upon findings from this and other studies, we propose that deletion and duplication CNMs in the human autosomal genome are likely to be generated in the proportion of approximately 2-3:1. We further postulate that intragenic gene duplication CNMs in other disease loci may have been routinely underascertained. Finally, our analysis of +/-20 bp flanking each of the 40 CFTR breakpoints characterized at the DNA sequence level provide support for the emerging concept that non-B DNA conformations in combination with specific sequence motifs predispose to both recurring and nonrecurring genomic rearrangements. Hum Mutat 31:421-428, 2010. (C) 2010 Wiley-Liss, Inc

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie